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1992 4.0 cutting out


poorwhiteboy

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My '92 4.0 5 speed is dealing me fits. 149k; has run flawlessly (but it's been pretty damn well maintained).
Lately; when it's first started; the check engine light is on. It runs rough; stumbles a bit. When it gets out on the highway and warmed up; the light goes out and it runs great. After a few miles; it bucks/stumbles; feels like it's backfiring; and the light comes on again. I don't have an obd tester; and of course; the dealer wants a minimum of $125 to look at it.
Ideas?
 


TxGasRacer

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Take it to AutoZone or one of the other chain auto supplys and they will pull your codes for you and it's free. Hope this Helps you out.
 

RonD

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Yes, you need to get the Computer(PCM) trouble codes.
Auto parts stores often have OBD II readers but not OBD I readers, your '92 is OBD I.
'95 and earlier is OBD I
'96 and up OBD II

But you can read these OBD I codes yourself :)
Under the hood usually by the brake booster is the VIP "test port" to read the codes, you can hook up a jumper wire(paper clip even, lol) to the test port and when key is turned on the CEL(check engine light) on the dash will Flash the code numbers in memory.
Write them down, don't "remember them", :) , "I think the code was.........", is worse than not having the code at all.

Read here first: http://www.therangerstation.com/tech_library/OBD_I.shtml

You can also use a test light or analog volt meter to get the codes.

As said in the article there are two sets of codes, current codes, and History codes, there is a 6 second pause before History codes are flashed

Code list is here: http://www.therangerstation.com/tech_library/2digitcodes.shtml


Common issue with Ranger 4.0l is dirty MAF although that usually won't turn on CEL
Clean MAF: http://www.therangerstation.com/tech_library/CleanMAF.shtml

From your description of poor cold running then a sweet spot and then poor warm running it could be the computer(PCM) is not getting correct information from the ECT sensor.
ECT(engine coolant temp) sensor has TWO WIRES, it is only used by the PCM, not the dash board temp gauge.
If there is a signal problem with the ECT sensor then CEL would come on.

ECT sensor on the 4.0l will be located just above the thermostat housing on the lower intake, it can be tested with a volt/ohm meter.
There will be 2 devices that look similar at that location.
2 wire ECT sensor
1 wire engine temp SENDER << this one is for the dash board temp gauge

But until you get the trouble codes it is all just guessing
 
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poorwhiteboy

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Well; solved my issue today. I purchased an Inova code reader off of craigslist for $10 (it stores all the codes so you don't have to count the flashes).
It was giving code 157 and 158; which are low voltage to the MAF sensor; and high voltage to the MAF sensor. Installed a new one; ran much better; but still had a little cut out. Pulled all the plugs (less than 1k miles on Bosch Platinum). Two of the plugs already had half of the electrode burned off. Advance warrantied them all; I traded them in for some of the new Efire plugs. I went ahead and replaced the two wire coolant sensor you suggested.

Truck runs great again; mileage is up. The code read and the manual are now in my glove box.

Props to all of you!
 

poorwhiteboy

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Forgot to mention; I did the driveshaft swap from a '97 Super cab; instead of cutting down the fuel tank guard; I put the '97 guard in.
Great tip; thanks again to all.
 

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